Active RFID tags are well known today. For example, the Matrics Group manufactures “MicroSensys™” Active RFID tags, and KSW Microtec manufactures “Smart Active Label™” Active RFID tags. An active RFID tag includes a small battery, and transmits RF signals via an integral antenna. The battery adds significant cost to the RFID tag. The RFID may be preprogrammed with information that represents, for example, the identity of the product which bears the RFID tag. The transmitted RF signals typically include the identity of the active RFID tag. If the active RFID tag includes additional data, the active RFID tag may transmit the data as well. An active RFID tag can effectively transmit to a receiver up to 100 meters away.
Passive RFID tags are also well known today. A passive RFID tag does not include a battery; instead, the passive RFID tag has an integral antenna which receives RF signals from an active RFID tag or remote transceiver. The transmitted RF signals power the passive RFID tag, i.e. the passive RFID tag captures the energy of the RF signals which it receives and uses the energy to drive transceiver and other circuitry on the passive RFID tag. The transceiver circuitry on the passive RFID tag transmits information, such as the identity coded into the passive RFID to identify the product which bears the passive RFID tag. The passive RFID tag may also include a memory to store any type of information transmitted by the active RFID tag or other remote transceiver. Typically, passive RFID tags have a range of about three meters.
It was also known for an active or passive RFID tag to include an environmental sensor, such as a temperature or humidity sensor. For example, the Matrics Group MicroSensys™ active RFID tags and KSW Microtec Smart Active Label™ active RFID tags include temperature sensors. The temperature sensor measures the ambient temperature, and circuitry on the RFID tag containing the sensor records information about the temperature. For example, if the RFID tag is attached to a temperature sensitive product such as a food package, the RFID tag will record whether the food was exposed to excessively hot or cold temperatures during shipment. The active RFID tag may also periodically record temperature samples over time.